Windows and glass panes in doors, panels and the like are a major source of unwanted heat loss and gain in a structure. With increased cost of fuel and energy, the moderation of unwanted energy losses on account of these structures has become of increasing importance.
One method of reducing heat transfer through windows has been through the use of double glazed, and even triple glazed windows. Double glazed windows make use of two panes of glass that are attached together by a spacer. In some instances, the space between the two panes is hermetically sealed and can be filled with dry air, or with a dry inert gas such as argon or nitrogen.
Although double glazing successfully reduces the energy transfer through a window, the use of two panes of glass substantially increases the weight of the window. Increased weight in windows is normally unwanted because of the need for heavier frames and sashes, heavier mounting hardware, and more rigid sash materials. Moreover, construction of double glazed windows is more complex than normal window construction, because the double glazed pane unit is constructed separately from the sash unit and then the sealed double glazed pane unit is mounted into the sash to assemble the insulated window.
An alternative to the normal method of assembling a double glazed window makes use of a sash unit that has the spacer for the glazing panes formed integrally with the sash. This innovation avoids the separate construction of the sealed double glazed pane unit, because the panes are mounted into a sash that has been formed from sash elements that include the integral spacer.
During the past several years, it has also become important to provide windows that are impact resistant. Many building codes, especially in areas that are at risk for hurricanes and major storms, now require impact resistant windows. In addition, blast resistance and shatter resistance has come to be important for windows in selected locations. A conventional method for the provision of impact and shatter resistance for windows has been the construction of safety glass. In this method of construction, a layer of durable transparent material, which may be a polymer, such as a polyurethane or polyvinyl butyral (PVB), is inserted between and adhered to two panes of glass to make a layered structure having glass on the outside and the polymer on the inside. Uvekol® may be used as the durable transparent material. When the window absorbs a blow that is powerful enough to break the glass, the presence of the durable polymer inhibits pieces of glass from flying in the direction of travel of the blow.
However, in many cases, the pane of glass separates from the sash. As the pane of glass is shattered by a missile, it tends to separate from the sash. The now shattered pane of glass separates from the sashes and enters the structure in the direction of travel of the missile, creating a hazard. There is a need to reduce the tendency of the pane of glass to separate from the sash, and also to reduce the tendency of the pieces of shattered glass from separating.